POL

#include<stdio.h>
#include<algorithm>
#include<stack>
using namespace std;

struct elem{
    int val;
    int I,J;
};

bool mycmp(elem a,elem b){
    return a.val < b.val;
}
int main()
{
    int n,m;
    scanf("%d %d",&n,&m);
    int table[n][m];
    bool visited[n][m];
    elem order[n*m];
    int idx = 0;
    for(int i = 0 ; i < n ; i ++){
        for(int j = 0 ; j < m ; j ++){
            scanf("%d",&table[i][j]);
            visited[i][j] = false;
            order[idx++] = {table[i][j],i,j};
        }
    }
    sort(order,order+(n*m),mycmp);
    int ans = 0;
    for(int i = 0 ; i < idx ; i ++){
        int val = order[i].val;
        int I = order[i].I;
        int J = order[i].J;
        if(visited[I][J])continue;

        stack<elem> st;
        st.push({table[I][J],I,J});
        int cnt = 0;
        int moveI[4] = {-1,0,1,0};
        int moveJ[4] = {0,1,0,-1};
    //  printf("Start (%d,%d) \n ",i,j);
        while(!st.empty()){
            int uv = st.top().val;
            int ui = st.top().I;
            int uj = st.top().J;
        //  printf("Go to (%d,%d) : %d \n",ui,uj,uv);
            if(visited[ui][uj])continue;
            visited[ui][uj] = true;
            st.pop();
            cnt ++;
            for(int k = 0 ; k < 4 ; k ++){
                int vi = ui + moveI[k];
                int vj = uj + moveJ[k];
                if(0 <= vi && vi < n && 0 <= vj && vj < m && table[vi][vj] - table[ui][uj] == 1){
                    st.push({table[vi][vj],vi,vj});
                }
            }
        }
        if(cnt > ans)ans = cnt;
    }
    printf("%d",ans);
    return 0;
}